My first "expedition vehicle" was a 1990 Honda CRX. I'm not kidding. I used to load that thing to the gills and a buddy and I would head off to the dirt roads of Eastern ORegon for days at a time. I put a roof rack on it, with a basket and even had a fuel can strapped to the top and to the back. Sometimes carry one of those car top containers that was actually longer than the car itself. Wish I had pictures of that.
I even went so far as to put a metal plate under the front of it to keep rocks from taking out the oil pan. When I ventured to a point when the road sort of went away, I hit a big rock which destroy my metal pan, but not my oil pan.
But it was at that moment that I decided I needed a truck. Back then, a 2WD Prerunner would have sufficed just fine as I mainly needed clearance more than anything. But I would have eventually upgrade to 4WD, because no matter how well set up a 2WD is, eventually you'll need 4WD. For me, I use it most climbing steep and sometimes hairy roads to lookouts and other sites or driving in the snow or muddy desert roads.
I'm not sure if any of that applies to you or not.
My take on it is this. If I had the Prerunner and there wasn't money in the budget to upgrade to a 4WD, I could definatley make the best of it as 90% of where I go a high clearance 2WD vehicle will do just fine. As mentioned investing in gear that is easily transferable to another rig makes the most sense.
But in the end, it's hard to argue that 4WD wouldn't be nicer to have.
So, in my opinion, it really depends on how money you have in the budget to spend on a vehicle AND gear. If funds are limited, since you already got the Prerunner, I'd probably stick with it. No sense going broke buying a new rig, when the one you have seems to be working out for you most of the time. But otherwise, I'd upgrade.
If you were to keep the Prerunner, I would probably invest in a winch, even a mechanical one, if funds are tight. Something to nudge you out of trouble, if needed.
You're Prerunner might also be a good candidate for an solid axle swap and you could install 4WD....if you dare.
Good luck.