I work at Best Buy and as far as I know, with in-store pickups there won't be any movement until the night before should the store receive your item. This probably depends on the store though. You'd then get an email saying it'll be ready for pickup the next day, or even an email the day of if it actually arrived.
If the morning starts, and you still haven't gotten an email then your item simply hasn't made it to the store yet. Please don't call a million times and ask where your watch is, and how much longer it will be (I was this customer years ago), we really don't know the answer to your questions as much as we would love to answer them. Do know that as soon as the SKU you ordered comes in, and you're next in line on the list for that SKU, a sticker gets put on it ASAP with your name and it cannot be sold to anyone or skipped for the next person in line. Our system doesn't work that way.
On the day of release it's still VERY possible that it will arrive on a drop shipment. I've seen this happen for big releases, and it just happened for the Note 8 launch. We had a customer who didn't get their specific phone the morning of the launch, but his device came in later on in the afternoon with a random shipment of phones.
I think the company just revamped their timing system, (we did for in-store pre-orders at least) and it's waaaay more accurate now. I think they learned from the S2 launch, but only time will tell.
I pre-ordered a S3 SB 42mm watch for in-store pickup too! I really hope mine comes in, and I have high hopes it will! I can't wait to see all the excited customers too coming in for their phones and watches!