Your language play amuses me, tuxgeo.
I'd been envisioning a seamless transition from Stonefast to whatever adventure we undertake next. If the Underdark, then I had rather thought ya'll would discover a quirky little tunnel in Stonefast that lead Down Below. If a wilderness campaign, I'd been thinking that ya'll might be waylaid in the open after leaving Stonefast.
That said, yes, if anyone wants to dump their Stonefast character and start fresh with a new one when we transition from Stonefast, that's fine with me. If I need to supply narrative to the effect that you guys return to Luskan (or some other locale) so that new characters can be introduced, that's fine, too. Those are all pieces that we can work out when we get closer to wrapping up Stonefast.
Again, it's early days for this discussion, but I can at a minimum confirm that I will certainly permit players their choice of keeping, tweaking, or ditching their current character. I can also confirm that I'm at least contemplating picking up Out of the Abyss; it releases September 15, which isn't that far off. The release date is the inception for my query whether ya'll are interested in adventuring in the Underdark. I saw the date and was all, like, "Oooh. Shiny. I wonder what they'd think of that?"