Hast fast will the size of block chain increase?
When the size increases too huge, it will be impossible to run the client with little hard drive.
Has the developer considered a solution to solve this problem?
1. depends on the number of transactions per block and how fast blocks are generated.
assuming current maximum block size (500KB) and current block generation rate (11/hour), we get a growth rate of 128MB/day.
realistically, for now, divide that by at least 10, as i haven't seen a block much larger than 50KB, and most are much smaller.
2. realistically, hard drive space is cheap, about $0.001333 BTC ($0.04) per GB (cheapest per GB is 2TB drives, which go for about 2.66 BTC or $80). at the above mentioned 128MB/day, that 2TB drive will store the next 40 years of blockchain, at which point a 2TB hard drive would probably be considered as out of date as a reel of 9 track tape is today.
3. there is a planned headers-only client, which would store much less data (only the block headers (about 80 bytes per block, i believe), rather than all the transaction data), though i believe it's still in development, as it generally isn't considered a pressing concern.
also, it's possible to prune blocks from the chain after all the outputs have been redeemed, though again, this hasn't been implemented yet, as, again, it generally isn't considered a pressing concern.