It wouldnt surprise me if the 1.6L V6 was switched out for something else.
However i am led to belive the V6s are not cost effective due to the energy recovery systems being employed. And this is one reaso why 2 well know manufacturers dont want to get involved. Its the 30 seconds of KERS and HERS as well as ambiguitys in the budget and cost controls for engines as well.
Personally they should have kept the current KERS system, but made it more powerful and more cost effective. Id have given them 125hp for 12.5 seconds a lap by push button. However id have given the engine manufacturers freedom over the V6, as long as it was between 75 and 80 kilos in weight, and was a standard length of 800mm and was a standard height of between 400mm and 500mm so that manufacturers could have differing V angles, also id allow VVT and all other electronic gubbins for increasing power and efficiency. Id make engine mounting and transmission mounting points standardised as well.
However id do one thing against the manufacturers, id make the turbo or super a standard part and also get a standardised fuel pump that pumps no more than 5 litres of fuel per 5Km, whitch would mean that fuel tanks would need to be no more than 61 kilos, however tanks would have to have a minimum of 65 kilos as to a standardised spec and have at least 3 kilos in them at all times during a event. The turbo would have to be able to give variable boost between 1.5 and 3 bar, so that drivers a tool to push their engines and such, and turbos shouldnt be allowed to be engaged by KERS and the super would have to be able to give 4.5 bar. Exhaust posistioning would be in a aerodynamically neutral posistion no more than 250mm rearward of the rear wheel centre line and no more than 200mm above the rear wheel centre line and no less than 50mm above the rear wheel centre line, and exhausts have to be no more than 85mm in diamater and cut flat.
This would give manufacturers enough to think about.
As for cost, a team that is linmked to their own engines (Mercedes/Ferrari) have to keep a engine budget of €50m a season and engines can go to no more than 2 more teams for a cost of €7m a season. However, engine manufactures that arnt linked to a team (Renault/Cosworth) can supply as many as 5 teams, and also must supply engines for no more than €8m a season. Cars can have up to 5 engines per season, used consecutivly, so an early season blow up will screw you up, same with a late season blow up as new engines require a 10 place drop at the first event of usage and a 5 place at the next event.
As for allowing the engines to be used in other series, why not, if it increases development and also gives the engine manufacturers more of a chance to increase the chances of recouping costs and such and making an actual profit.
Who wouldnt want to see a DW12 with a Ferrari in the back of it at Indy or a LMP1 Lola or old AMR1 with a Mercedes in the back of it at Le Mans? Id also allow for GP2 to use F1 engines, however they get 2 per year and a 2.5 kilo per 5 km fuel pump and a 25% smaller turbo, thus meaning they have better chance to learn F1 tech at a lower level. Cost for outside F1 is unlimited, however GP2 would be limited to €2.5m per team for 6 engines per GP2 season to include GP2 test days as well.
Ideally im looking for a engine to do 3000km in F1, GP2 and Indy spec; 8000Km in LMP spec, however LMP could have bespoke turbos or supers with a bespoke fuel flow limiter.
With theese rules, Manufacurers would have plenty scope for showing relyability and speed, and also plenty of commercial scope to actually make a profit. There is enough to constrict and contrive, but plenty to make the manufacturers to showcase their own tech and have a engine that was different to the other ones in the garrages next to yours.