It is true that vasectomy can be reversed. This is usually done with microsurgery to bring the two end of the vas deferens together (vasovasotomy) or to bring the vas to the epididymis (vasoepididymostomy). However, vasectomy should be regarded as an irreversible form of contraception. This is because reversals are not always successful and if a man goes into a vasectomy expecting it to be successfully reversed later down the line, he may be proven to be disappointed.
An alternative to vasectomy is sperm retrieval which maybe offered by specialized fertility clinics.