Universal has said that they will replace free-of-charge any of the BTTF2 and BTTF3 discs that anyone has in February when the new pressing is complete, so there is no need to hold off buying them unless you want too. (The fixed discs will also be in stores. Hopefully they'll have a different sticker or something to differentiate the two versions).
Here is what Universal has said so far you need to do to get the replacements. Universal is expected to release a more formal statement next month.
Send your BTTF2 and BTTF3 discs too...
Back to the Future DVD Returns
PO Box 224468
Dallas, Texas 75260
Need to include:
Name
Full Mailing Address
Daytime Phone
Reason for Return (improper cropping of BTTF2 and BTTF3)
Package Discs up without the case
You should get your replacement discs sometime in February they say.
The scenes that are cropped wrong are not the whole discs, just a few select scenes here and there. Even though it's unfortunate this happened (apparently Universal wanted to get these on the shelves for Christmas), at least they are providing an alternative to get the fixed discs at just the cost of shipping them to Universal.