OK, that's a theory on the web but I highly doubt that he will gain a Yonkou status.
I mean the Yonkou are somehow tolerated by the WG, but Luffy did various things the WG can't tolerate:
- hit a Tenryubito
- broke into ID and freed various dangerous criminals
- disturbed the war
- is the son of Dragon
Bare in mind though that Whitebeard, big mom, Kaidou and Shanks were all prates on the grand line that made a nme for thereselves and were once rookies too. They have probably comitted crimes the WG does and never will tolerate AND being a pirate alone is allready a crime so I don't think they actually tolerate them. I think the WG is just not strong enough to erase them.