InnoDB has been the most popular MySQL Storage Engine as the MyISAM Engine was not usable for most use cases due to its limitations. MySQL AB was working on Falcon, the successor of InnoDB and MyISAM, for quite some time already.
After MySQL has been aquired by Sun and the Falcon chief architect left the team it didn’t look too good for MySQL already. But after the announcement of Oracle going to buy Sun everything is open again.
Personally I think its looking quite bad for MySQL, especially after InnoDB has been published as standalone database. Looking at the whole product portfolio of Oracle in the database segment now is very confusing. While it has been discussed the last days that “MySQL” could survive as “small Oracle” I think that the situation is much clearer now: There is nothing that is on the upside for MySQL. Many “MySQL” installations already run exclusively with InnoDB. It just fits better into the strategic portfolio of Oracle, making it the ideal small business solution. There is no need for MySQL to be the small brother of the big “real Oracle”.
But still doubts remain and we will have to sit and wait the future brings. But while sitting and waiting we can have a look at our existing installations and evaluate what requirements they fulfill and what features of MySQL we really use. Then we are prepared for whatever Oracle will decide.