Yes, it should work, but I would put a resistor between the emitter and ground to pull down the Pi's inputs.
The Pi's inputs are all high impedance, so almost no current will be taken by them.
That means you can put many in parallel with no problem, in terms of DC performance.
However, they will each have capacitance, as will your wiring, and that will slow down any transitions, particularly negative going ones - you could end up with them reading high long after the input has gone low.
Putting a 2.2KΩ resistor to ground will discharge that capacitance, ensuring a low registers as a low.
It will also reduce the effect of any interference pick-up on your wiring.
I had to look up the MB102 on your diagram. For anyone else reading this, it's a power supply that takes in 5v or more and regulates it to 3v3.
http://www.petervis.com/Raspberry_PI/Br ... upply.html
It's not obvious what happens if, as in your diagram, a mA or so is fed into
the supply's output. That could happen because, with the signal from the Arduino high, and no load on the emitter, current into the base can only go out through the collector.
This is another good reason to provide a load on the emitter.