Bob, it's entirely possible for them to grow large enough to mill into boards. If they are isolated there is a greater chance. Depending on how badly you want them to grow into large trees you can treat them with injectable pesticides. Be sure to monitor for any signs of DED and remove infected trees/ branches. See more information at http://ipmguidelines.org/TreesAndShrubs/content/CH03/default-5.asp#...
I planted two supposedly blight resistant American Elms about 5 years ago, looking for a good shade tree, and to help preserve the species. They were the "Princeton Elm" strain. (An interesting coincidence, since I probably walked right by the parent tree or trees while in college in the early 80s).
they were about 6 - 8 foot tall and 1" DBH when I planted them. They are growing quickly, now a solid 4"+ DBH. It's probably too soon to tell if they are blight resistant or not, but I'm hopeful. The only trouble I've had is that they started to tip a few degrees about a week after the remnants of hurricane Irene gave us a good soaking. I staked them up, and now have been gradually loosening the ropes over time so they'll develop their own support (at least that's my theory/hope).
Update: My two Princeton Elms are now coming up on 10 years since I planted them.
I left the ropes that were staking them up after Irene on for several years, putting a bit more slack in them each year before I finally removed the ropes completely.
They are now about 60 feet tall and almost 12" DBH, showing no signs of Dutch Elm disease. Here's a picture of one of them:
There are a number of American elm in my neighborhood that are doing well, but we do lose them to DED - some go when only a few inches in dia. while others are 24 " dbh and still doing fine. Elm is moderately hard and stiff, and very shock resistant. I've heard farmers say they used it for barn flooring, stalls, and wagons because it resists breakage. Should be interesting to make some lumber. If any do die and you want to fell them, don't wait long. They quickly get brittle and dangerous. Good luck.