Maybe, maybe not. Come back in about 3 years. Honestly all kids are different (especially gifted ones) and they don't all progress according to the books. If crawling is skipped though you need to be really creative in finding ways to crawl now as the cross patterning is important for the brain - also other cross patterning stuff. Just try and enjoy you child and talk to them a lot.
Yes to the wait-and-see. Just have to mention, though, that the available research does not currently support crawling as a necessary step in brain development. Crossing midline and visual-motor integration, of course, are both quite important, but early walkers-who-skip-crawling generally find lots of other ways to cross midline without special treatment.
I have plenty of training and clinical experience in child development (so I do have some idea of what is "normal"--and it's a pretty broad range), and I, too, had to resist the urge to continuously mentally-assess my children. If you want, keep a monthly (don't overdo it!) journal of interesting milestones or anecdotes about him, in the event that it might be useful retrospectively, but put most of your energy into enjoying the innumerable moments of discovery and accomplishment that he is experiencing every day. You're clearly spending lots of focused time with him; he will show you what he needs for stimulation.
