I am sure they would not pass up an opportunity to upgrade you. I have a two-park BGTB/SWO pass, but that’s how it started. Check with guest services at the front of either park.
Right now, large banners within SeaWorld encourage visitors to upgrade to an annual pass to be among the first to ride Infinity Falls, still under construction and opening late summer. I received an email in April to sign up for that.
If you decide to upgrade and visit this month of May, the AP perk o’ the month is a free passholder lanyard with a sealed badgeholder, so the paper card won’t get soaked on the water ride. One side of the plastic bears the logo for Infinity Falls, with a tiny SeaWorld logo on the other side, placed just so it keeps blocking the bar code. I need to flip the pass upside down to fix that before my next visit.
Another perk of being a 1-year, 2-year or platinum passholder, as you might already know, is you don’t have to pay to $2 fee to go up in the sky tower. Still must go through the queue and get the badge scanned at the Sand Bar, then you get the comp ticket.