Technically, yes, he could stay in the U.S. until the I-130/I-485 are adjudicated. The problem in this case is two-fold: on the one hand, we don't know whether F2A category will remain current for long (I will not be surprised if a backlog will develop again by the end of the first week of August, and USCIS will stop accepting simultaneous I-130/I-485 filings); on the other hand, if you marry your boyfriend less than 3 months after he entered the U.S. on a tourist visa, USCIS will accuse him of a visa fraud (that he deceived the U.S. consul when he said he was coming to the U.S. without intention to stay here, while intending to marry you) overcoming this presumption of fraud is not impossible, but isn't easy, either. You should find an immigration attorney who would help you see this case through, and discuss with him/her the path you should take.
Answered on Jul 25th, 2013 at 1:45 AM