Do have references for either of these new parenthetic claims? Because there is only one signalling voltage for SD cards, and two for SDHC, and they appear to have no direct relation to the class system. And the last official statement I saw was that the SD incompatibilities were being looked at, not that there were no plans to try to fix them.
SDHC (including Micro SD) and SDXC are based on 1.8 volt technology due to narrower traces deposited during the fabrication process, vs. the wider traces associated with the 3.3 volt technology used in original SD cards. 1.8 volt technology introduction made possible the debut of higher capacities starting at 8 GBs and, given the higher capacities and narrower traces, higher speeds are possible owing to lower current and associated lower heat generated in the traces. This was a necessary development as SD card capacities increased along with processor, bus, and other I/O interface speeds (e.g., 1 GB/s Ethernet). So, there is a coincident overlapping correlation between higher capacities and higher speed/Class SD card interfaces.
The SD card interface on the R-Pi can"t generate the commands to shift the interface between 3.3 and 1.8 volt mode without a hardware upgrade, per Eben"s Q&A answer toward the end of the April 4th webinar/Ebenar.
Recall that price is _the_ predominant design factor in the R-Pi, hence USB 2.0 not 3.0, 100 Mb/s Ethernet instead of 1 Gb/s, 256 MB RAM rather than 512 MB, 700 MHz ARM11v6 vs. 1+ GHz v7 Cortex multi-core, etc.
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!!!