Doubtful.
1) No way they would get him through confirmation - at least not without him promising to recuse himself.
2) Sessions was a loyal supporter who risked his political capital to endorse Trump early and gave up his Senate seat. I would hate to see him out in the cold. Sessions is also more conservative than Rudy, although Rudy would have been my ideal pick for the job.
3) If Trump wants Sessions to investigate something, I believe (correct me if I’m wrong) all he has to do is order it. Trump needs to order it.
The President can ask his AG to investigate anything he wishes, but he can't order him to do so. Also, during his confirmation hearings, Sessions told the Senate judiciary committee that he would recuse himself from any investigation of Clinton's email server or the Clinton foundation. He claimed that, because he'd called for a Clinton investigation while campaigning with Trump, it would place his objectivity in question.
Trump could insert a replacement during the August recess. They could serve until the end of 2018 unless confirmed by then. There’s a whole lot of recess appointments that should be made next month. Lots!