Purchasing the Season VIP Pass will unlock additional items such as mascots, kits, emojis etc. as well as other benefits which can be read about on the Season VIP message box.
Some of the benefits of Season VIP are for the current season, like package timer reductions, season point multipliers etc. At the end of a season, if you decide to purchase the Season VIP, none of these will apply.
NOTE: Purchasing the Season VIP, does not unlock the Season Pass