I doubt IBM will part with GBS. That’s where the announced go forward strategy resides. (see IBM annual report) Rather I believe they will trim/sell the old GTS parts.
Most of these are now encapsulated into TS&C. (again see the Annual report pages 40-48). Yes they put it in writing. The CFO said the same thing in the post earnings call with Analysts. (listen to Kavanaugh call on stock holders relation page) I would be looking for IBM to exit outsourcing (your mess for less).
The high IBM burden rate along with innovation not being able to help enough, is just too much drag vs the Indian outsourcers. IBM also showed their hand via not renewing IGF Oem contracts effective 6/30 (see annual report). This means TSS OEM is also in the mix