Yes, I agree that MS (and Sony, because they said so) will take some time before continuing with meaningful acquisitions.
But at the same time, I think they won't miss good opportunities if they suddenly appear, specially if are "cheap" and "small" companies that would be pretty helpful for them for a little cost (as the recent Sony acquisitions of iSize or Audeze).
Regarding having issue with regulators, I think only the acquisitions of EA or Take 2 could raise their eyebrows but they are smaller than ABK, so if they allowed MS get ABK very likely would also agree the acquisition of any other considerably smaller publisher if MS is who does it, specially if they wait some years and continue releasing many games on PS and if the ABK acquisition -as expected- doesn't highly push the Xbox and GP numbers.
I think regulators would be way more aggresive against Sony trying to acquire a top publisher because they are the market leader in consoles, non-mobile game subs, console VR and pretty likely cloud gaming. Specially if Sony keeps improving their marketshare vs MS and maybe also if distances from Tencent as the top 1 overall top grossing gaming company.