French Apple blog iGen has acquired a copy of an internal memo from retail chief Angela Ahrendts to retail store staff explaining that all orders will remain online only through the end of May.
Supply is definitely tight, so if you're looking to get one, your best bet is probably to place an online order sooner than later. Mine should be arriving fairly close to April 24th, as I got my order in very early, but most watch models are now showing as shipping in June. Apple is likely overestimating the delay in order to manage expectations and avoid disappointment. I would recommend ordering online, and then booking a try-on appointment in an Apple Store. That's the approach I took. If you don't like it in the store, then you can cancel your order. You should have lots of time.