I believe the regional news has also been delayed to 7 maybe 7:30 in the past. BBC One only has half an hour scheduling that they can discard tonight really (Question of Sport), whereas BBC Two has more flexibility, I think they will switch to BBC Two at 6pm as normal, but we'll see. We've not had a really late Murray match in the second week this year whereas I can remember in past years the BBC One schedule being cleared for Murray through to 11pm.
Personally I'm of the position that a match should start and end on the same channel without interruption.
If need BBC One can clear it's schedule up to 7:30pm, at which point they'll need to show the regional news. The One Show has been known to move to BBC Two when needed, and similarly the 6pm national news has also been known to occasionally shift to BBC Two (post-DSO).
The current situation now depends on if Roger wins this third set. If he does, regional news will not be long after it's ending, and the One Show will remain on BBC One. If not, the Regional News will be 7:30pm and The One Show will become the Two Show.
Expect a flurry of tweets from the BBC Regional News programmes within the next half hour as they work out what they're going to do.
Nations can do theirs on 2. I suspect BBC 2 England will slip in a Coast at 6:30, with the English Regions at 7:30 at the earliest, following the tennis (could be a while if Murray is to win)