unfortunatelly seems this not available right now. Lets rise RFC. But before I fill the jira - let me know also if you need to disable only Enter key or also Up/Down arrows (full keyboard disablement)?
To be totally honest - the only key which has a major usability impact (in our scenario) is the enter key (people filling in a form and wanting to submit it without the completion occurring). If the user uses the arrow keys, chances are they're going to want the option...
One possible other approach: the selection box appears but nothing is selected by default, until the user keys up or down and then hits enter to select the current item - so the keyboard navigation is still there - but an item has to be explicitly selected before hitting enter selects anything - if enter is pressed after moving up or down onto an item, then the current behaviour is completely reasonable.
Sorry for the ramble - I'm thinking on the go here about the consequences of something I'm not 100% up to speed with.