Dragons of the Third Age

[Eurytus]

"550-597. The dates of 'the last war of the Elder Days' were changed to 545-587, and after the last words of the original entry the following was added: 'Ancalagon is cast down by Earendil and all save two of the Dragons are destroyed.'" (HoME XI, 3, V)
This quote from the Tale of Years is unambiguous as to the dragons surviving the fall of Angband. They were Scatha and Smaug.

I wouldn't say that this quote is necessarily unambiguous. It references Earendil casting down Ancalagon and states that all save two of the dragons are destroyed. These two statements are linked and so can be read as all but two of the dragons present at that battle are destroyed. This does not exclude other dragons having left Angband earlier in my opinion.

Also, on a more general note I find Tolkiens HOME series as not necessarily satisfactory as regards resolving issues. He was writing and rewriting to such an extent by that point that he may have changed his mind several times over and still not come to a definitive result.

Seven the Dwarf-kings possessed, but three he has recovered and the others dragons have consumed.

And I think that the above quote, already posted here, would certainly indicate the presence of more dragons.