I just bumped into this thread and only quickly parsed on the naming convention for this feature. Personally I find the … very terse and more importantly extremely hard to parse as a human. In previous threads an alternative name was pitched that seemed to also go a similar path as any/some keywords. As we already speak about parameter packs, it would be almost intuitive to also introduce pack T instead of T… which seems to be context dependent. On top of that T could still be surrounded and further extended in the future:
Bikeshedding example:
pack T[42] // hypothetical pack limit