I know with some of the OHV parks getting closed with the help of probably well-meaning (but politically misguided) environmental groups, that off-roading doesn't look like it has a bright future in the States and/or the rest of the world. I see, however, some reasons to disagree with this conventional wisdom on the future of this 4x4 past-time:
1. Closing down State OHV parks is going to cause 4x4 drivers to get resourceful and actively encourage private landholders to develop property that has potential as off-road trail(s); private landholders -- who might also be 4x4 drivers -- might voluntarily initiate development without any encouragement from other off-roaders. This might mean nothing more than the owners simply cutting out a trail up rocky outcrops or creating dirt roads, etc -- basically nothing more than parks typically already do with their respective trails.
Yes, you'll probably get charged a fee to use a private trail (got to cover insurance, salaries of personnel on site, marketing etc). But between the normal expenses of gas or cost of trail damage to your rig or upgrades, dropping $40 to use a private trail probably isn't going to kill anybody.
2. The average Joe or Josephine, young or old, age 16 to 120 can go to the Jeep dealership and buy a new or used Jeep Rubicon. With its electronic lockers, 4:1 transfer case, solid D44 axles, 32" tires standard, these things want to be used off-road. And this is a factory vehicle!
We are not talking big numbers here, but the Rubicon is a gateway ride (think "gateway drug" ). First the owner tries an easy trail on a weekend, next he is planning a week long trip out of D.C. to Tellico, N.C. Then he is driving across country to Moab and decides to relocate and setup a 4x4 shop so he can get the newest parts at wholesale
Also, the new 2007 Jeep Wrangler JKs -- including the JK Rubicon -- are bigger, more comfortable and have fricking 4 doors most of the time!? So, you are going to start seeing the young, active family-deal out on the easy trails, etc. Then "Dad" does some justifiable upgrades and next thing you know he wants to hit the challenging trails.
You also have the flex-fuel, bio-fuel/bio-diesel powered engine angle which will head off much of the enviro-griping over the next 10-20 years as these engines are likely introduced in Jeeps, Toyotas and other vehicles. The military and special forces are actively looking at these types of alternative fuel power-plants also.
And you have the fact that a ton of different trucks are now coming with locker(s), big tires, decent suspensions. For example, you have 3+ versions of the Hummer when only one existed 5-6 years ago. That vehicular hardware is going to want to get used.
3. Baby Boomers. The healthy 60-65 year old folks that I know dig physical exertion, active life-style stuff and want to have some fun. And some of them are going to want to stay outdoors and go off-roading. After all, even if you have a bad back you can still drive in a Jeep Jamboree
The follow on to this is the whole NAFTA deal with regards to the Sun-Belt states. If more boomer retirees start becoming ex-pats/dual citizens in Mexico -- the current trend -- then you are likely going to see more favorable living conditions down there as money flows that way. Expect to see Mexico reach more for that Boomer market and the adventure tourism market; This might mean, more, new, readily- available off-road playgrounds down south. For Yanks, it'll be like, "hey I have all the Mexican Trails in the GPS, lets just cross the border and I'll get a a street-by-street to the trails just like this was San Diego."
If you are on the street, get off-road. That's where a lot more people are going to be in the future, despite state-run OHV park closures.