There is a possible reason NOT to use direct injection. It looks like under the 2017 tier 3 emissions standards (which phase in from 2017-2025) they may be needing exhaust particulate filters, and then those will need a regen mode just like on diesels. In the end you end up with no MPG benefit and a huge cost addition.
http://sam.abuelsamid.com/2015/09/01...issions-rules/