OK, so here's some additional reality to ponder. I know Mr. Son personally, as he occasionally attends the National Model Railroad Association (NMRA) local meetings for the Coast Division of the Pacific Coast Region, i.e., the NMRA division which includes Silicon Valley (and you thought corporate DoubleSpeak was nonsense!). So, your first data point is that Mr. Son is a life-long model railroader - he's one of us - a totally complete geek!
When Softbank built its offices in Silicon Valley, it didn't put up yet-another brand-new shiny building that looked like every other one built that week. It renovated one of the former railroad station buildings along what is now the Caltrain commuter route that uses Union Pacific trackage and rights-of-way up the San Francisco peninsula from Gilroy, and through San Jose. So, your second data point is that Mr. Son understands big pictures. He has a real and healthy appreciation for history, including architecture, as do many Japanese, wealthy or not (I lived in Japan for 5.5 years, BTW).
Mr. Son has been away from Softbank after turning it over to a successor who turned out to be a typical business school idiot, and is the one primarily responsible for that upwards of $100 billion in debt. Mr. Son built Softbank from essentially nothing into a premier, world-class technology company, and not just a large Japanese telecommunications company, as the media incorrectly report. So, your third data point is that he is a very shrewd, intelligent, and patient man, and he is not one to do stupid things. This deal was not just a knee jerk reaction when the Brexit vote happened, either - he's been eyeing ARM for two years, and Brexit simply made the decision a fait accompli because the price was irresistible. I can see him laughing about how easy it was made for him.
Softbank isn't Mr. Son's only interest - he hasn't been off being a typical billionaire out yachting, jet-setting, and otherwise hobnobbing with "celebrities", unless they have money they insist on giving him, and even then, he's not available to such people on a social basis, it's just good business. So, your fourth data point is that he has principles and he sticks to them.
Mr. Son not only stated that ARM will remain in Cambridge in perpetuity, but he plans to double it in technical personnel alone over the next few years. I can't say 100% that will happen, but I will tell you this - I'm a military man, and I would put my life in Mr. Son's hands. The civilians Out There won't understand a whit of what that means, but my fellow Brothers and Sisters in Arms certainly will. So, your fifth data point is that there's no such thing as a true sure bet, but he's about as close as you're ever likely to come to one.
I don't know what his inclination will be wrt the licensing fees, but I'll repeat my previous observation. He is a very shrewd, intelligent, and patient man, and he is not one to do stupid things. Raising the fees would be a very stupid thing to do, especially with 95% market share. ARM didn't get there by overcharging their customers, and he's not about to do that now. So, your sixth data point is that his statement about doubling the size of the technical staff in Cambridge (not Mumbai, Shenzhen, etc., you'll note) tells me that he's planning on expanding ARM's market well beyond their nearly-saturated dominance of the mobile device market. I won't say what those expanded markets are because I intend to make some money through some shrewd, intelligent, patient investments of my own, and I don't need any of you clowns jacking the prices up on me until after I've bought low, and will later sell high thanks to uninformed late-comer market-followers.
As noted by others, a large debt by this kind of company is not a big deal, and will be less of a deal as Mr. Son works on the problem, so that's your seventh data point. Apple has had more cash on hand recently than the entire U.S. federal government, and who do you think is more at risk of collapsing, especially watching what's been going on at the political primaries and conventions? Word has it that tickets out of the U.S. starting November 8th are now non-existent at any price - the entire airline, business jet, passenger ship, railroad, bus, limo, Uber, and Lyft fleets have been bought out, regardless of which candidate lies, cheats, and steals the election. I suspect that some tickets will show up on ePrey, etc., but if you have to ask the price, you won't be able to afford them.
For those tut-tutting the loss of another great British company, it was never British to begin with from a financial standpoint - the technical and management principals who founded it just happened to be of that lineage, but not the investors. I've never been in ARM's Cambridge offices, but I'm guessing that its diversity reflects that in their offices that I have been in elsewhere, and they're about as diverse as any current Millenials-oriented ad pablum you're likely to see, except for the ratio of women in the technical departments - that's a problem pretty much everywhere. There's your eighth data point.
One thing is for certain - we are definitely fulfilling the Chinese curse/blessing: "May you live in interesting times."
The best things in life aren't things ... but, a Pi comes pretty darned close!
"Education is not the filling of a pail, but the lighting of a fire." -- W.B. Yeats
In theory, theory & practice are the same - in practice, they aren't!!!