Be Wary Of Collecting Currencies, Engrams, and Postmaster Packages
With The Dark Below and House of Wolves DLCs, many people saved up their postmaster packages. When they would receive rewards from the cryptarch, vanguard, or crucible as well as engrams, they would save them in hopes that they would provide an early chance at new content. In both cases this did not work. While this is not a guarantee that this won’t work in Destiny’s The Taken King, it’s probably a pretty good sign.
If you want to save those items up anyway for the purpose of dismantling them and/or exchanging them for other materials/experience, then that makes sense. You can also keep your factions at the point right before they level up and push them over after The Taken King releases.
One of the aspects of Destiny that has changed a few times between the game’s DLCs and patches is how different currencies work and for what they can be exchanged. So far, it seems as though the game provides you some sort of reward for your old stuff. So they will probably still give you something in The Taken King. But this is not a guarantee in year two so be prepared for anything. According to Planet Destiny, “Legendary marks replace “Crucible” and “Vanguard” marks. “Armor Materials” replace Hadronic Essence, Sapphire Wire, Plasteel Plating.” So it may be worth maxing out your crucible/vanguard marks to buy new weapons, even if you need to trade them for legendary marks first.
Although, if you’re going to bet on anything, motes of light and glimmer might be a good idea. Once again, it’s not a guarantee, but motes of light have been valuable for one reason or another since the beginning of Destiny and we have not seen any indications of that changing. And, according to Planet Destiny, you can use “glimmer to order a new Legendary weapon, and Wednesday that weapon arrives with a random set of perks.”