Yes they should. They should be able to buy vendor weapons and armor and partake in Trials of Osiris [i]but[/i] their rewards should be suspended until TTK is purchased. If I were a businessman that's what I'd do. I see no harm in this small incentive to continue a relationship with an avid player who's hesitant to expand their experience. Nor do I see an ill effect towards those who've already paid for TTK. It must be confined and conditional otherwise no.