Ghasem, the uploaded Steemit images are currently stored at Amazon Web Services, no IPFS involved at all, currently! ;-) Whether any of the data on the steem blockchain will remain in the future, simply depends on the witness nodes hosting the Steem blockchain. A blockchain is not something "magical" that's always there: there are 3 forms of internet storage infrastructure possible:
-a- centralized, like a normal client-server infrastructure where 1 centrally hosted server serves multiple clients;
-b- decentralized, currently like Steem, where anybody could, but only a few people do so, here called "witnesses" host a server node, forming consensus via an algo (POW, POS, POB, "gossip protocol", etc) about the validity of blockchain data
-c- distributed, where any computer can be a client or a server: like IPFS.
I suspect, in the near future, that Steem will be ported to run on EOS, which uses IPFS, and then, we can say there is a distributed infrastructure hosting the Steem blockchain. But in any case, it could happen, that zero nodes host the blockchain, and then of course both the service and the data is "lost", as is the case with a central hosting infra where the host server node is offline (permanently).
Thank you. Very informative answer. But my question was somehow different. What I asked was that is it possible that in a future hardfork it will be decided to discard some of the old data in the blockchain?
The nature of blockchain hashing is - in simple terms - that each block gets signed with the previous block-hash. In essence that means to sign block N only block N-1 is directly needed, but N-1 blocks [N(0)..(N-1)] are still needed to form consensus ("for a re-check" of hash validity).
There are always situations possible, although rare, perhaps, in which all blocks need to be iterated over to gather data. For UA for example, to do it right, I have to go over all blocks and check for follower (follow / unfollow) mutations to eventuelly come to the conclusion that you currently follow who you follow. I need all blocks / data for that.
For daily news feed browsing, old data is hardly needed of course.
So possible... maybe. Probable... hardly.