Existing software will need to be recompiled - meaning converted into a language the CPU understands - to take best advantage of the switch to the new multi-core processor.
Yes it's an ARM v7 quad instead of V6 single. There's the rub. That will likely take awhile.
But meanwhile it will do what the current models do at about the same speed.
My B+ is overclocked to 900 mhz, currently, so performance will remain competitive. Also it will be fine as a dedicated CNC Interface board until the time comes to plunk down another $35 for some other purpose.
The big question to me is when will they come out with the long promised cheap touchscreen?