I'd definitely wait since it's only a matter of weeks. No one really knows what the improvements will be, but faster and quieter and cooler running are my guesses. Many other parts of the machine are already perfect.
Just wait. At the very least I'd expect it to run faster and cooler.
Plus if you find the improvements aren't significant you'll likely be able to get a SP3 at a cheaper price than now.
Are we sure about cooler? The new skylakes are still 15W like the sp3 ones were, so the thermal potential is the same. So possibly faster and longer battery, but similar thermal issues. Or because they've updated the integrated GPU, it might remain cooler for CPU focused tasks.