The other possibility is that we'll have a home game on the 31st October or 1st November in the League Cup - that's the earleist we could possibly open the stadium. A couple of days after the City game which the club said they felt they might have been ready for but couldn't commit to - if things have gone well since then it's a possibility, and would likely be a much lower-tension game to open with than Chelsea.
Good thinking - but I think what makes it unlikely is that unless Spurs announce within the next few days the dates of the test events there will not be enough time to hold them before the dare of the next round draw (which will be within a day or two of the 26 September when we play Watford), and before the draw we need to notify the League cup organisers before the draw which venue we will hold the match in (as we did nominating Milton Keynes last time - and cannot change after the draw is made).
So just as Spurs said 26/29 October v ManCity might be possible but couldn't commit to, I think the 'lead time' and timescales to hold test events might kill this date too - unless as I say Spurs announce that we are going for this date (assuming we get a home draw) in the next few days.