Fwiw, our repo is about 60-70% converted to py3. We’re on pants 2.4 and cant upgrade to pants 2.5 since it drops support for the pip legacy resolver (which from some earlier testing i performed last Feb was much faster for py2 resolves - potentially just an artifact our our py2 dependencies and not a general issue but still..). That said, i think a pex major version bump to drop support for py2 seems reasonable as long as we can pin to a pex via download-pex-bin that supports 2.7 as an interim solution.
Unfortunately, its unclear to me when we could be fully off 2.7 because we use the apache aurora project and its still on 2.7, and its been moved to the apache attic. We could potentially just freeze that to a separate repo if need be though.
Anyway, i dont want our needs to trump the larger needs so as long as we can get a pex to support 2.7 then we should be good.