1) Will it happen? Peter has said, VST3 will come as a free upgrade in 2024.
2) Why the delay? PGM always takes the spring/summer to port BIAB to Mac code. (a different major topic in itself)
3) Is it easier in another framework? Partially true if you're talking about built in VST3 libraries but then you're talking a complete host rewrite. (another major topic)
4) How much of VST3 functionality? This can cause it to take longer. There are VST2 to VST3 wrappers available that can make it available soon, but not a great long-term solution. Supporting some of the VST3 capabilities multichannel outs, dynamic inputs, sleeping, window resizing, and auto categorization would take longer.

One of the main reasons that people jump to a DAW to finish their song, besides a more comfortable workflow, is VST3 routings in particular. If done right VST3 with its extended routing capability would keep people in BIAB longer.

Studio One (latest version), Win 11 23H2 , i9 -10940X 3.3 GHz, 32GB Mem, a 4K 40" monitor, PreSonus Studio Live III Console as interface/controller. secondarily test on Reaper, Cakewalk, and S1 on Surface Pro 3 Win 10 (latest versions).