I think gas engines are a viable alternative right now, but to stay under the 5Kg limit is the big challenge. If enough interest is generated in gas powered pattern ships then somebody will make an engine to fit the current regulations. It may be pricey at first, but if it is successful the price will probably drop some.
If the cost of fuel is really that big a deal then fly a .90 sized plane. There are several great kits available (especially from Japan where .90 sized planes are considerably more popular than here in the USA).
As for the future - I don't see any radical changes in the near future. The equipment we have now is fantastic (I started flying in 1969) and priced quite reasonably. The single most expensive item now, seems to be the kit itself. However, there are still some reasonably priced kits available (the EMC, the Hydeout, the Entropy, the Temptation). MK has just released an all wood 2 meter kit (the Topstar) which should cost less than $500 delivered here in the USA.
Older designs still fly very well. The secret to success in competitive aerobatics is still PRACTICE
See you at the practice field!!