I believe that quads, mx bikes, jet ski's and all that stuff we love will remain gas/petrol, for a few reasons.
1 Lets face it compared to cars and trucks the amount of quads and our other toys in the world is tiny, this means that there is less of an impact on climate change. This means that unless our governments decide to simply ban them which is very unlikely in the USA but i could imagine it happening here in the uk
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, because of this i don't believe the manufactures will dump loads of money into research and develpment in this relatively small market unless they are forced to and we will just get more efficient 4 stroke engine.
2 All of our toys are toys and therefore we are less worried about mpg we just want them to be fast and fun, because of this i currently believe that gas/petrol engines are the only form of propulsion that off the fun factor. This will probably change in the years to come but not in the near future, HEV is a very good alternative and we will still be able to simply fill up the tank almost like we do with gas/petrol/diesel but we will only be able to fill them up from the pump because hydrogen is filled while under pressure. But again there will have to be a lot of reserach and development to put these into our toys and i just don't believe anyone will be willing to pour the amount of money in.
3 Battery is still a big no in my opinion we would be going backwards as insted of simply filling the tank up when we run low and then carry on we would have to charge batteries which could take hours and hours for 10 mins riding, add that to the conditions our toys are used in makes them even less likely to take over gas/petrol engines. Although a hybrid is a good idea for our toys i don't think it will work just because of the size issue and again we are less concerned about mpg than we are about more POWER and mpg is a hybrids main points not power.
I can see diesel being used more and more in utility vehicles and the 4x4 quads which in my opinion wouldn't be a bad thing although i don't want them to completely replace gas/petrol just have them as another option until the performance is just as good as gas/petrol just because we still use 4x4 quads and things like the yamaha rhino for fun as well as for ultility.
As for cars and trucks i believe that we are heading towards HEV which i think is a good idea, its just as convinient as gas/petrol/disel in form of filling up and driving for as long as we want without having to charge batteries and then drive 5 miles before they run out. Also using and electric motor in the HEV should be very reliable because there is only 1 moving part in the motor, although there will be a lot of electronics but there are in our cars already. Yes we all love the smell of petrol burning and the sound of an engine but i think as a daily drive HEV is a very good idea and maybe having gas vehicles for the weekend and for fun, because lets face it many peoples average drive is stuck in traffic on the way to work not blasting down the road doing 150mph. Hybrids are a posibility but i think they are not going to be used as soon as HEV become more peopular because they still use gas/petrol/diesel and its very complicated and not that much more economical than normal engines.
But who knows maybe we will get flying cars that run on air in the future and all of this will become obsolete lol, just my 2 pence.