I'm not sure about the DEC price continuing to spike, at least because of the Chaos Legion packs. The Untamed packs could be purchased with credits (tied to USD), in addition to DEC. Nobody is going to be paying DEC unless the price drops down close to the peg. I don't think the Chaos Legion release will necessarily lower DEC costs, but I wouldn't count on a huge spike.
On the other hand, I'm happy to hear that there is going to be another DEC-only collection (similar to DICE), which will help to prop up DEC prices.
Good luck, and congrats on taking some profits!