A product line changes to reflect the needs of the consumer over time... It's only natural.
If people don't buy the SLE, it will be discontinued, or made an option, I'm sure.
All the recent changes you've seen in the Rev products (no mylar, etc) have come from flier input... The SLE is no different.
To be fair, there are a few people who like the SLE spars... So, I'm sure they'll always be available, if not standard in the kites.