It depends if future updates fall under the category of expansion or not. If future updates are expansions then certain KS backers of 80 GBP or more should get them. If they are termed paid minor updates but not significant enough for expansions then perhaps not. But I am betting we will get them for free. We will see and if not, a big can of complaints of course.
KS page quotes:
https://www.kickstarter.com/projects/1461411552/elite-dangerous
" Pledge £80 or more
Digital Download Pack. This includes a single digital download of the game, and any expansions, and all the other rewards above except those requiring physical delivery."
and
"+£80 Have an additional Digital Download Pack. This is effectively the same as an additional £80 pledge tier and includes any future expansions (Delivery March 2014)"
and
"The £80 pledge tier and higher now also includes free expansions for Elite: Dangerous! For more information on likely expansions check the Development Plan video further down the page."
and
"Really big expansions are likely to be paid for while we also intend for some smaller free updates. If you have pledged to to £80 tier or above you will receive all expansions for free."