Ed,
there are no turkeys on my land but are encroaching. Slightly further south turkeys are everywhere. I can't think turkeys can be good for grouse just like relatively recent arrival of turkey vultures was not good for ravens or crows. 40 years ago there were basically no turkeys in this province but since then has been a very successful joint Canada/US reintroduction effort with numerous agencies and volunteer groups. This was an extremely productive undertaking and the introduction of open seasons was greatly enjoyed by a lot of hunters. Now all those birds are Ontario-born and they're here to stay and spreading further.
Whether that is bad for grouse on my patch I really don't know but would rather not find out.