It depends... Can you spot that 90 mph fast ball anywhere in the zone? How are your secondary pitches: Good change, Curve? Possibly a filthy slider?
If you can compete with the best, and show poise on the mound, you can make it!
Reaching 90 is great, but there are plenty of people throwing 90 plus now... Think along the lines of uniqueness, or showing something that you may posess that others may lack. I'm sure there are people throwing 95 plus, but don't have the mentality to pitch in the big leagues.
I don't know, I guess it depends on the circumstances, and whether or not the scout/managers thinks you have potential. Anyways, I wish you the best of luck! I, too, hope to pitch 90 plus someday!