Probably. They tend not to make separate discs for rental market. When you've rented the DVD you were renting the single disc version which didn't included special features. You'd be missing the special features if you bought that version too. The Blu-Rays are all one disc, so if you rent it, then you should get everything on that disc.
They didn't early on, but I'm seeing it more and more now. Sometimes they even have "Rental" printed on the disc itself.
One movie I really wanted to see some special features for was Social Network, but all you get at either Redbox or Blockbuster is just the one, bare-bones disc.