There are two tweets from Pete Hines pertinent to the conversation.
I'll quote them and add the links.
It was discussed by LoneVaultWanderer and is also addressed in this video: https://www.youtube.com/watch?v=bE8FSbSaakI
First, Lone asks Pete: 'hey Pete, just a question. Are we able to level up all SPECIAL attributes to 10 if we keep playing long enough in Fallout 4?'
Pete replies: 'I believe so. What you do with your points when you level up. You could only increase your SPECIALs every time'
ref: https://twitter.com/DCDeacon/status/647521913611399168
In another tweet, VaultofDaedalus usefully follow this up:
First, Daedalus asks Pete: 'So essentially instead of taking a perk you could use that unlock point to raise an attribute from say 5 to 6?'
Pete replies: right. 'So if you never pick a Perk you could max out by level...43? If my math is right?'
ref: https://twitter.com/DCDeacon/status/647523427994222592
Upshot: you can continue to drop level up points into SPECIAL ranking instead of perks.
However, that's not the whole story.
While you could spend points raising SPECIAL to 10x7 at level 43,
the usual efficient way to level is by collecting bobbleheads.
With a set of bobbleheads, you could max SPECIAL at level 36.
IF as been speculated you can level up with a collection of magazines (is there proof of that?)
that might mean you could max SPECIAL at level 29.
If the magazine theory is right, you can max all SPECIALs and perks at Level 299.
If it's just bobbleheads that additionally increase SPECIAL then it will take you to Level 306 for full max.
Has anyone heard more about magazine collections increasing SPECIAL ?