Does the vow become void if its condition is not met at present, with the possibility of it being met in the future?

The reference for a vow (nadhr) is the intention of the one making it. If the intention was limited to a specific year and enrollment in the college did not occur in that year, then fulfilling the vow is not obligatory. However, if the intention was to enroll in the college in any year, then fulfilling the vow becomes obligatory upon enrollment. If you do not enroll in the intended college, then nothing is required of you. It should also be noted that making a conditional vow is disliked.