In previous series we have had something at the end of the first episode to lead into the main arc / storyline for that series. Maybe it will be the same next year.

5.1 The Eleventh Hour

Amy's wedding dress is hanging up in her bedroom. S5 was all about the reset for the universe taking place on Amy and Rory's wedding day June 26th 2010.

6.1 and 6,2 Impossible Astronaut / Day of the Moon

Doctors "death" at Silencio, Amy's pregnancy revealing the identity of her and Rory's little girl Melody/River who grew up to become both the Doctors "killer" and his wife.

7.1 Bells of St John start of Clara being the Doctors "impossible girl"

8.1 Deep Breath

We see Missy welcoming Robot man unto her twisted version of "heaven". Describing the doctor as her "boyfriend" and claiming he loves her.

Last year we had Missy coming up with a "idea" so she will be back at some point.
Might have a few red herrings as well though. Moffat likes to trick us.

What i think will happen.

Missy gave Daleks knowledge on the Time Lords, and in Frontier in Space style also trap The Doctor, which will lead to one massive fight and potentially the re start of the Time War. But in reality Missy played them all along, stuff happens Daleks defeated, Gallifrey restored, Missy regenerates and The Doctor may or may not regenerate as well. And Billie leaves due to the death and destruction.

You heard it here first.

Well the start of Series 7 was actually Asylum of the Daleks, but at any rate that was also obviously alluding to the main arc of the series with Oswin showing up.

Series 9's opening story then referenced the hybrid which was the sort-of arc for the series. The whole story touched upon the recurring themes the rest of the series went on to explore.

It would make sense for Moffat to start plotting quickly in Series 10, both as he's got form for doing so and as he's only got the one series to play with this time. He may even start plotting in the Christmas special this year...so long as bloody Nardole isn't the story arc I'm cool with whatever

Nardole is Susan?

The Doctor should regenerate along with Missy

1. They both should end up looking the same

2. They are dressed the same and regenerate but not look the same.

end of both 1 & 2 Missy gets up 1st and goes to the TARDIS and Missy tells Billie I am The Doctor .

I love when a new series starts and everyone is in speculation of whats in store for us in the endgame. Time to look for key phrases.

I am hoping for a low key story arc this season, one that doesn't involve re-writing the show's continuity or the Doctor's personal timeline.

It is SM's final season, expect a massive arc and unfinished arcs to also be wrapped up. I worry he'll over do it and the season will be a bit of a mess.

That doesn't sound like SM at all.

Oh, wait . . . .

Can't we just have a series of 'ordinary' stories? Just like the show had in the 60's & 70's?

I'd be up for that, although I think a lot of people like the trail of 'breadcrumbs'.
Breadcrumbs do not maketh an arc by the way.

All we can do is wait for the fashion for arcs to stop, as it will. Like all TV, one show does it, the others all copy it till it's done to death, then the next fashion comes along.