I'm neutral on the matter, since I've never been a fan of Forgotten Realms old or new. Fortunately,
4E research is something I've been doing a lot of... but I haven't seen much that the bulk of fans of the Realms will like.
In short summary of things most relevant to the Rotunda in particular:
Forgotten Realms as a whole is in for a 114 year time jump from the currently published Campaign Setting Guide. It will completely overshoot the worst period of the Spellplague, wherein the majority of arcane spellcasters will be negatively affected in dramatic ways (death, insanity, general asplodedness... unless they're within a Mythal, which still work without the Weave, go figure) as the Weave is annihilated by Mystra's death at the hands of Cyric and Shar.
There's talk of opening "time gates" so that characters converting to
4E can jump ahead in time via cheesy deus ex machina that wouldn't be needed if they'd have actually let the Forgotten Realms remain the Forgotten Realms, and not some mishap of a new setting with old names.
The vast (and I do mean vast) majority of Faerunian gods will be either killed, merged, or ignored. Projected trimming of pantheons looks to be going from 150 pre-
4E to around 25 post-
4E. Included in this are racial pantheons, which seem to now be down to one actual deity and a bunch of "aspects" of other, human-centric deities. Thus far, Tymora seems to be around, but with the slash-and-burn action going on, things don't look good for the luck goddess.
Waterdeep itself is in for massive cosmetic changes, including an upheaval of some massive construct that runs amok downtown and winds up a statue. The Lords seem to still be around, but none of the ones that are currently known (there's mention of the Blackstaff's heir, but that's all I've seen so far). The city still exists, but it's not the same city that the Rotunda relies on right now. There's also that matter of the orc kingdom in the nearby area, that for some reason has been written to poorly resemble the 1960s civil rights era thanks to Salvatore.
Aside from that... what else do you need to know about the changes? I've probably got more stored away up in the ol' noggin that can answer any questions right away; I've certainly read enough of the updates out of morbid curiosity on what they're doing with their former cash cow.