From DBs perspective, why operate expensive electric locos when you have plenty of relatively cheaper to run and maintain (with better parts availability) 66s available...
A lot were parked up needing heavy exams or expensive and time consuming parts replacing (016 needed a new transformer for example). As for 017, even if it did ever return (which is pretty unlikely now) it likely wouldn't remain in Stobart Rail livery due to DB no longer having that contract and Stobart Rail no longer existing as it once did
For one relatively short distance working (given DB 92s don't run on 3rd rail anymore so it would be either be Wembley-Daventry or spend even more money reinstating 3rd rail capabilities), it just doesn't make financial sense for DB. And in today's world, DB Cargo are storing serviceable 66s due to lack of work so they aren't going to splash out on 92s if they don't desperately need them. Until/if more profitable work suitable for a 92 shows up, the active fleet will likely only remain at Dollands Moor for Channel Tunnel work.
And all that is coming from someone who'd love to see DB 92s back on the WCML, just don't think it'll be happening again in the near future though unfortunately