I think he’ll get there but there is no way MD can put him over the top. Only about 260 delegates are available rest of this month and Trump will need about 500 more. Most likely CA and NJ put him over top on June 5.
Even if Trump falls short, Rubio and Kasich will have about 400 delegates between them. Trump will make a deal if he has to. Hopefully he’ll get the 1237 on his own so he can pick his own VP.
Plus the VP does not really matter as far as winning an election. Most everyone, except the most ardent Trump supporters, see Trump losing in a landslide. Why would Rubio want to be part of that.
Trump should be close to 1,100 + by the end of May, and if that happens and he wins NJ with 51 delegates, he'll need only about 70-80 out of kalifornicator, montana, newmexico and southdakota which have 228 delegates.
Doesn't seem too improbable to me.