Here is a graph of "What We're Waiting For" versus time. It shows all of the announced but not released, non-accessory SKU numbers (including the base game) since X-Wing began. If an thing is announced, the line gets a "+1". If a thing is released, the line gets a "-1".
A few things of note.
Currently we are at a "February lull". This may last until April or so, if the last two years are anything to go by.
Only once before have we had less stuff in the pipeline (announced but not yet released). We have been in this same position (only waiting on a single SKU) twice before (not counting the time in 2011-12 when we were awaiting the base game itself).
It appears, over time, we are usually awaiting 4 things, give or take. This makes sense, as we are usually aware of a single unreleased wave (plus a bit, occasionally) at a time.
Oh, the glory days of July, 2015, when we were aware of 10 items loaded in the pipeline! (Wave 7, Wave 8, Imperial Raider, and Imperial Assault Carrier).
I would guess we could comfortably get to a 6-8 item pipeline by the time Gen Con announcements roll around in August. This probably does not include the C-ROC, actually, which I predict will be released in early June (based on the 145 days the Imperial Assault Carrier took between website announcement and release). This could easily mean 2nd Scum Epic, Scum Aces, Rebel Veterans, and a four-ship Wave 11. Could even be something more like Wave 11 (announced April/May) and Wave 12 (announced August).
