to the Dell smartphone roadmap, Android Central managed to get their hands on the tablet roadmap as well. The roadmap features a bunch of new models including the Gallo, Rosemount, Sterling and Opus One, Silver Oak and Peju.
The Streak 10, also known as the Gallo, should be coming in April, running on Honeycomb. In addition to Gallo, Dell is apparently preparing an update for Streak 7 as well. The next one is Rosemount, a 10-inch Windows 7 tablet with a 1366x768 screen and a release date set for June. The Sterling is the one with the least details in the roadmap, but according to the position in the roadmap, it looks like a successor to the Streak 7.
The Q1 2012 will apparently be quite interesting for Dell as CES 2012 should bring Opus One and Silver Oak running on Android Honeycomb and the Peju, a Windows 8 based tablet. Once again, the positioning in the roadmap suggests that Opus One will be a small one, Silver Oak a mid-sized and Peju should be a 10"+ sized tablet.
Of course, bear in mind that even if these leaks are 100 percent real, Dell will certainly make an adjustment or two 'till these show up in retail/e-tail, so nothing is carved in stone.