Most likely your rootstock you've ordered should be ready for grafting, why wait if you can graft this year.
Get your scion wood now before it's too late and save them until you're ready to graft.

bass

I like to wait until the tree has established roots able to push nutrients into the scion before grafting, for that reason I prefer to wait until next year. My feeling is that the tree is already stressed by the transplanting, and why add any more stress by grafting now. Al

Sounds like it wouldn't hurt to do some this year and plan to save some rootstock for next (plus propagation). Thanks!

Do it this year. That rootstock should have sufficient roots to support the extra couple of buds that you'll be grafting onto it. :)

yup, this year....without a doubt.

Some rootstocks are difficult to benchgraft. G30 is one, because the wood is somewhat brittle. I was advised against it, but tried anyway as an experiment, and had a low take rate. The failures took buds really well the following summer. If you want to experiment and have fun with grafting, why not try some bench grafts, and bud some others in August. You'll want to graft your bench grafts about 4 to 6 weeks before planting, so just hope your delivery cooperates on that schedule. When you bed your bench grafts, use damp sawdust inside a plastic bag, not sealed completely. Store in the dark at 50 degrees F. Plant them when you would plant your tomatoes. Since you are in Zone 4, that's rather late in spring I suppose. Don't worry if they don't take. You'll get another chance in August. As a rookie, all my summer buds have taken. The only problem is finding budwood at that time.