The USBR's latest forecast for next spring indicates a low of about 3505 in March/April of 2023. We've pretty much hit the high for the year, which might creep up to 3539 (or 3540 if you're an optimist) before beginning a steady decline, which always happens from late summer through the following spring. The Bureau expects the lake to be at about 3525 on October 1, and just a hair under 3520 on January 1. The rate of decline through next spring will be pretty typical in terms of volume, but because the lake is pretty low, the same volume loss results in a slightly greater decline in surface elevation--hence, a 30-35 foot loss rather than the more usual 25-30 foot drop over the winter.
Then all will depend on the snowpack to see what happens next spring/summer.
As for Bullfrog access, others may know more, but I imagine they will still have the marina operational when it's at 3505, although I'm not sure what the status of launch ramps will be at that point. The NPS maintains this page that they update to discuss low water impacts to their facilities:
Changing lake levels
www.nps.gov