It had been said (kcnole remembering something Lee said in a previous thread) that Disney was financing the descent, not Siemens. Someone else can confirm whether or not that's true, but if it is then there's no reason Disney can't move its money elsewhere. Were I in a position to make that decision, I would pull money off of the descent also.
Also - it's possible (nay, likely) that Disney's agreement with Siemens is for a yearly attraction budget, and Disney's fiscal calendar rolls over at the end of September (it looks like Siemens does as well, but a quick search didn't confirm it). A couple things could be happening right now.
1) Disney is/was financing the SSE work because Siemens wouldn't. I'll call this unlikely. Any agreement would include budget for incremental plussing, and Siemens would be obligated to pay.
2) Disney blew through the budget from Siemens for the fiscal year, and won't get more money until October 1st. Possible, but I don't think they would have missed it by this much. But hey, crazier things have happened.
3) Given the unprecented economic climate, Siemens and Disney sat down and renegotiated the yearly budget to reign in costs. Most large companies are doing this, or have done this recently, and these two shouldn't be any exception. They most likely agreed that Siemens could reduce sponsorship funds for the short term, with an agreement to increase them over time (were I Siemens, I'd try to get Disney to do that). The funds likely work out to a similar, or larger amount over the long run, but in the short run it contains costs.