Ianal, but my sense is that as long as they keep trying to hold back the tide, they're eligible for trademark protection. Once they give up, there's nothing to stop Google Docs Photoshop mode, Microsoft Office Photoshop, or rflrob's awesome photoshop. Though there's nothing that says that vigorous enforcement needs to be mean—see, for example, Jack Daniels: https://brokenpianoforpresident.com/2012/07/19/jack-daniels-...