There's been a discussion today in the DL forum, presumably going to be reported in AF/FB too but I haven't yet found the thread, that AF has changed the rules regarding the required fare classes to use miles or SWUs for upgrades on AF operated flights. At this point, some have been told that the DL W fare class for premium economy will not be upgradeable any longer (into Affaires). The reported change might also impact upgrade eligible fare classes on AF tickets. I don't have further details, but it might be wise to check your tickets and call the airline if needed.

ADDED. One report is that "AF has ended the upgrade program, at least temporarily."

Presumably this does not apply to the SkyTeam upgrade program, although that can require FULL Y fares and the existence of the PV cabin on AF complicates the rules for upgrades.

SWU upgrades on KLM now require Y or B fares; M and U are no longer allowed. I would assume that this also impacts upgrades on KLM metal using DL miles but this hasn't yet been mentioned in the new thread on this in the DL forum. One person had a confirmed upgrade on KLM with an M fare rescinded (but the ticket apparently hadn't yet been reissued); he/she was given the choice of paying $1400 to upfare and keep the upgrade or being rebooked and confirmed into BE using a longer routing on DL metal.