I'm starting to think that we will have at least 3 new Previews possibly 4 before June.
We have have the Preview on the 18th and seeing as GW confirmed that the first 2 have shown off about half of what was expected at Adepticon, then there is the chance that there is also a 4th Adepticon Preview, that is unless they've decided to ditch announcing some things in these uncertain times, which is very understandable. This could take us up to April 25th if they dont skip a week.
Then in May we should have the Warhammerfest Previews, now we dont know how large this is but I think its safe to assume that this will be split into 2, with a week or two gap in between the Previews taking us up untill June.