Nigel,
My apologies I missed your point.
I thought you were saying that they may not come at all and questioning the route in general. This could always be the case that it does not happen, as with any route news, but there seems to be more evidence they do want to serve MAN than not. Probably a bit like Air India at BHX. When it was very first mooted, probably many said 'believe that when I see it'. Saudia is MAN's version of that, having served here in the past too.
I agree that I doubt they could fill 7 B777's per week, but 3 weekly should suffice for any O&D as well as some connections. I would suggest the main driver of the route, especially as a B777 is being planned rather than the A320 that other smaller European markets see, is cargo.
We have a Saudia Cargo B747 visiting again on 2nd Sept, so seems the cargo market is indeed a big part of the route.
On a separate note, it is good to see growth in the cargo market again. Its no secret the cargo figures for MAN have made for some pretty dire reading, but Saudia running the odd B747 flight, LH cargo expanding again (will be 4 weekly as opposed to 3 this winter), China Airlines cargo looking to return and Cathay becoming more regular again (had cancelled many flights over the start of the year) points to an upturn at long last.