JMHO....let the Wankel and diesel die and concentrate on high output/high MPG engines. They should also get cracking on combining Skyactive with Electric motors for a hybrid and use that as a steeping stone to a fully electric car too.
Disagree on the HCCI.
HCCI, if they can make it work, beats hybrid in a big way -- there's a $3,000 battery (that's heavier than a dead priest as well, and accelerating mass does bad things to your fuel economy) you don't need, nor do you need the electric motors and switchgear. Yet both are going to get into the same efficiency area quite easily. Consider a "6" with an HCCI engine that can get within spitting distance of 50mpg @ 65mph. Impossible you say? Nope -- very possible without any further aero improvements. Hybrid will win in stop-n-go city driving due to regenerative braking, but that's it. That puts the current "6" in Prius territory in terms of fuel economy and yet it's a hell of a lot larger vehicle for materially less money
Hybrid ultimately loses due to the extra energy conversions. No way around that one, it's physics. On top of that it loses (big) on money simply due to the additional components required. If you amortize acquisition cost + per-mile fuel and maintenance the HCCI engine vehicle wins BIG.
If Mazda has managed to actually make HCCI work they will slaughter
anyone making hybrids -- they'll have a vehicle that costs
$5,000 less (to make!) at an equivalent trim and quality level, that sells
for ~$6-7,000 less, and yet returns equal or better fuel efficiency and performance.
That's fairly simple math, and it explains why they're after it. The other guys all know the math as well which is why they've all been after it to one degree or another.
Mazda can quite-easily go from a "small" car company to a monster with this engine tech if they have actually figured out how to make it work. That's the key "if"..... and it sounds like those crazy Japanese may indeed have figured it out.