No, you can go ahead an rank up the cryptarch and save the packages is what I'm saying. Once you open them after TTK drops, the engrams will roll as TTK gear. You do NOT have to edge cryptarch rank to see this benefit.
Old engrams and Cryptarch/faction packages will always decrypt to old stuff.
They are getting their Cryptarch and factions right about to the next level. About to roll over. They way they are set to get new packages sorely into the game with new gear. They includes getting the Cryptarch right there, with a few engrams saved for launch. Decrypting those, Cryptarch rolls over, package - goodies.
Not calling anyone out, because I honestly don't know what the right answer is, but I'm fascinated that this stuff is still debated.
Surely there's a definitive answer (at least historically) about if it's necessary to edge Cryptarch?