The Stimulus committed a Billion or so to upgrading from near Chicago [Joliet] (Aurora) to near St Louis (more or less Alton). Everyone understood that was enuff to chew on for Phase One, and anyway they weren't ready with plans and permits for the Phase Two stuff right then.
Then after the mid-term election of 2010, Congress in its wisdom aborted the plans to further invest in passenger rail, because after all, Obama was for it and that meant the Crazies were agin it.
When or if funding ever materializes for the now phantom Phase Two, the CHI-[Joliet] Aurora segment will get the full 110-mph upgrade treatment: double tracking, new bridges, grade crossings fixed, fencing, etc.; and the [Joliet] Aurora -St Louis segment will get complete double tracking etc. That way Phase Two, costing about another Billion, will cut another 30 or 40 or 50 minutes out of the run time. At that point more frequencies will be added, and the Texas Eagle presumably will be allowed to move at 110-mph speeds. By the time Phase Two is finishing up, we might even see the Horizons replaced by new cars of one level or another. (A Phase Three could include a new bridge over the Mississippi among other projects to shave more minutes from the schedules.)
Anyway, no problem that can't be fixed by time and money and clear thinking in Congress. So don't count on any progress for the foreseeable future.