Well, there's a couple of things you can do... if you keep them, they'll still be useful in year 1 activities and in crucible (they will scale). They may even be able to be used to infuse your new TTK weapons. If you shard them, the materials can get you more glimmer and motes of light from the speaker, which will be a useful currency (more so than now). The weapon parts will be used to up rep and upgrade weapons. So... it's kind of up to you. Both have benefits and downfalls...