Sam, from experience Gregorio knows that sometimes people read questions on Trulia when the question asked is not exactly their question, and take the word as gospel. I have also found him always to give appropriate answers, and be very helpful.
Seeing as I personally don't do many FHA loans at all, I thought I knew the correct answer, which is Gregorio's, but didn't want to chime in because I was not sure. Giving a quick answer isn't always the right answer. One of the problems on Trulia is that you get an e-mail from them within a very short time from when you ask a question asking you to pick a "Best Answer", so you don't have all the correct answers before you do that. Clearly others have given incorrect answers as well.
Dn, there are 2 issues here also, the main one being that you are talking about 2 years from now, and guidelines change all the time, so what the correct answer is today may not be the case then. Also, this might be the kind of thing that is an underwriter's call. They can determine if your situation will fit into the increase in family size or relocation guideline. When you are ready, ask to have a loan officer speak to their underwriter about this. To accomplish this, you would probably be smart to contact a local mortgage banking company that underwrites its own FHA loans.