A 60 gal
tank being 48" in length should suffice for a start but I would not wait two years to upgrade the size. How fast the bannerfish grows will greatly depend on other inhabitabts it competes with for food and overall continued health.
All things being "ideal" I would say it would become cramped after 6-12 months in a 60 gal
As far as other fish possibilities, I would instead suggest something that does not get above a max size of 5-6".. It would depend moreso on what type of tank yoiu wish to have as well?