What Appcelerator did not offer was an IDE to develop such applications. Instead they has a small tool for creating and packaging Appcelerator projects. Now with their acquisition of Aptana we can expect to have a powerful IDE to go along with this SDK.
Appcelerator plans to have a version of Aptana Studio with the Titanium SDK integrated by the end of March. Additionally, they plan to release Aptana Studio 3 which has been in beta for a long time, finally, also in March.
This bodes well for Titanium developers, however it is unclear what will happen to features such as Adobe AIR and Nokia WRT support, as their own product provides similar features.