Well , AKAIK for magento 2.2.x version , specially on design side you can consider this technology stack as an final iteration like js,xml and all ..
because from magento 2.3 onwards they are going to release PWA.
for PWA frontend framework might different as their visualization is different then regular website visualization but yes keeping their existing Luma theme and blank theme as it is ..
so as of now you can consider this as an final iteration .. but yes updates may came with this .. but not technology stack updates ..
Hope it helps !
For Magento 2,There are not many major changes will be available in magento version 2.3.* for Theme level.
They will introduced PWA concept for mobile theme. They will introduced PWA and they will used react js for this purpose. But for other themes like luma and blank they will not doing any major changes.
But we can't predict for next release of magento 2.4 and up version in future for any changes related to Theme for stack technology. Its very early to predict or any comment for future release with technology stack but upto 2.3 they will not doing any major changes in luma and blank theme technology stack.