I’m reading with great interest here and in the general media about the Southwest Chief’s possible re-route. Are there any other LD routes (or sections thereof) in dire jeopardy of being re-routed?
No.
One that seemed to recently escape a reroute is the Empire Builder around Devil’s Lake.
Yep. MSP station should be moving sometime next year, but apart from that, no changes.
Another might (possibly?) be the Cardinal although I don’t know if there are any viable alternate tracks.
Currently, it looks like VA and WV will upgrade the Buckingham Branch to keep it going. Nobody's suggested a viable alternate route. A shorter connection to NS at Charlottesville has also been proposed (would save 15 minutes, IIRC) but nobody's seriously developing the proposal.
Are the Zephyr or Coast Starlight in any danger of being re-routed off their respective routes through the Colorado mountains or along the California coastline?
The Zephyr intermittently reroutes between Denver and Salt Lake when there's track construction, but is in no danger of being rerouted permanently.
The Coast Starlight is certainly not going to be significantly rerouted; there are no viable alternative routes (the freights *really* don't want it on the San Joaquin route).
Here are the reroutes and potential reroutes I know about (looking at all trains, not just LDs). First, the ones which involve station changes.
* The Vermonter WILL be rerouted through Massachusetts; losing Amherst, gaining Holyoke and Northampton.
* As others have mentioned, the Cascades and Coast Starlight will be rerouted between Tacoma and Olympia to a faster inland route through Lakewood. This will also mean relocation of the Tacoma station to the Sounder station. Yes, the right-of-way is designed for double track service, although it will not initially be double tracked; this makes it better for future service than the permanently-single-tracked tunnels by the waterfront.
* There are serious proposals to redirect the Sunset Limited within the LA metro area to follow the Southwest Chief (losing Pomona, gaining Fullerton), after the Colton Crossing flyover work is finished.
* Springfield, IL is probably going to have the tracks and station moved to 10th St; still unfunded so far
* There are speculative proposals to redirect the Ethan Allen Express through southern Vermont instead of New York, but they keep not being funded.
* There are serious, but unfunded, proposals to reroute all trains to Richmond through Richmond Street Station
* There are serious, but unfunded, proposals to reroute all the Michigan trains between roughly Michigan City and Chicago -- but nobody's settled on a single route, so I don't expect this to happen any time soon. This would affect one station at most (Hammond-Whiting).
Next, the ones which do not involve station changes:
* There is a serious, but unfunded, proposal to reroute the CONO/Illini/Saluki within Chicago, as part of CREATE (no station changes)
* There are multiple proposals for rerouting of the Texas Eagle/Lincoln Service between Joliet and Chicago, and between Alton and St. Louis (unfunded, no station changes).
* There is a funded proposal to reroute the Texas Eagle between Dallas and Fort Worth (no station changes) which is being held up by negotiations over insurance.