No one can tell what things will be like next week let along tomorrow I think - has the mass of migrants gone and are they trying to board trains - I would think they are still there some anyway - but check the Hungarian Railways web site for current status of trains and or replacement buses.

http://www.mavcsoport.hu/en

currently on the home page it says "trains to Austria are restricted; train to Croatia suspended". - sounds like screening for bona fide passengers and not refugees but not sure - but check it and get updates.

When we were there, they had bused a large numebr of the migrants out a couple of days before our train was scheduled. There were still many (I can't even imagine how many were there before some left), but they mostly were in the lower level of the station, where it connects to the metro. They were not trying to board trains or interfere with service in any way that I noticed, the day we left.

Our train was to Prague, which was not one of the directions they were interested in going, but Vienna is, so the situation could be different. When the service was stopped (earlier in the week we were there), our train was still running, but did not stop at Keleti, so we would have to board at the next stop (in Slovakia). We had arranged for a taxi to take us there (for about $70). Turned out we didn't need to do this. But there may be a similar option for trains to Vienna.