It won't reduce the numbers. Every single person I've talked to says they will just buy the Deluxe for a few bucks more per month. Sundays have always been crowded here, especially in the Spring when there is typically another So Cal deal like the 2fer or the even better deal this year. Then as late May gets here it's worse as their expiration date gets closer to use them. Then go to Disney having more off-season events such as HalloweenTime, there is no slow time in September or October anymore. Slowest time I've seen there over the last 3 years is the first week of December.
Let's face it, if Disney was truly worried about crowds, they would not have any promotions at all. By suspending sales of the So Cal pass all they have done is created demand, and a worry, thereby getting more renewals than ever before. Or more Deluxe sales.
To the OP: Get the So Cal Select, it is worth it. When you get off work, go on Friday night. They are open to midnight usually. Then when you get a vacation day,take a Friday and go then. It is such a cheap deal, barely $16 a month! And you get the first day to use any day you want, even the Saturday or Sunday you want. At $16 it's less than most other entertainment these days!