I am experiencing bug #41416 when emerging ppp-2.4.1-r14 on a fresh system (gcc34-amd64-2004.1). 2.4.2-r2 is marked -amd64 because there was a problem with one of the beta ebuilds compiling back in December (AFAICT from the ChangeLog), but it compiled fine for me. I suggest marking 2.4.2-r2 ~amd64 and getting it into stable ASAP to avoid this QA bug. I'll report success/fail using it with rp-pppoe once I get to using it in the coming few days.
2.4.2-r2 should already be ~amd64 now, but if you think it should be pushed into stable i'll do that instead. i already have used rp-pppoe with it.