Look out for Carakan (apparently prononunced "Jarakan"):
we have now taken on the challenge to once again develop the fastest ECMAScript engine on the market
Fans of fancy effects may also want to look out for Vega, Opera's new hardware accelerated vector graphics library.
I doubt that these will make it into Opera 10, but hopefully we'll be able to get something out there for testing later this year.
There are a lot of other major and probably completely unexpected things going on for both desktop and mobile, but I'll have to wait until something is officially announced before I comment on it. Needless to say, working at Opera is very exciting these days.