I agree with the $2M/base number only for a couple of reasons -
1. adidas was recently downgraded. They've hit a wall. So, yes, they could over-spend to ramp back up again and pay Sydney $5-$10M/base, but we are in a era of prudence in sport spending.
2. NIKE is also struggling. They are single-digit growth in NA, and once again, when you're paying Ronaldo $30M/year alone to wear shoes, they are pretty tapped out in terms of major spends after getting the NFL, NBA, MLB, and all the other major soccer clubs.. those are close to billion dollar investments. Even Lebron is $1B.
3. There is no way ASICS, Brooks, Under Armour, New Balance, etc., pay the money necessary to land McLaughlin. They don't have the resources.
4. PUMA could be a player. They've been on the up, but not sure what has happened with Bolt's contract, which was in the $7-10M/year range. If they have exited that contract or downgraded it to ambassador status, she may be in play.
5. Li NING or any Chinese manufacturer (361)... could surprise. They have billions to spend and could be uber aggressive to land the next face of track and field. However, would be up to Sydney to take the money or not (like many athletes now face, i.e, D Wade $25M/year to play in China; Donovan, etc.)