I could not find an existing thread on this, so I'm starting one.
Work has been going on for nearly a year now. I-26 between I-126 and US 378 has been shifted up against the median barrier (and the westbound far right lane closed) so that earthmoving operations can commence. I don't think any work on the Saluda River bridges has started yet.
They have also just begun working on the I-20 interchange with US 176 (Broad River Rd), which I believe will be a DDI with a brand new longer overpass to accommodate additional lanes underneath for the I-26 interchange.
I believe a contract has been awarded to expand the I-126 interchange with Colonial Life Blvd to a full interchange, which, when completed, will function like half of a DDI, and it will allow for the permanent closure of the I-26 interchange with Bush River Rd.
They have not yet started on the I-20/26 cloverleaf. It will be converted to a turbine interchange.
All in all, I-26 will be at least 8 lanes from Harbison Blvd to US 378 (7 miles), I-20 will be at least 8 lanes from US 378 to at least US 176 (at least 4 miles, but probably longer), I-126 will have the expanded Colonial Life Blvd interchange, and pretty much every interchange within the widened I-20 and I-26 areas will be modified in one way or another.
This is all from memory. SCDOT does have a website dedicated to this project:
http://scdotcarolinacrossroads.com
Fixed link, needed HTTPS.
https://www.scdotcarolinacrossroads.com/
It's nice to see all these much-needed projects finally moving forward in South Carolina.