Can blockchain size become a blocker for bitcoin adoption? When I run bitcoin-qt, I noticed that it is taking lot of time to download recent blocks. It gives me impression that the more transactions, the bigger the blockchain. Even today the download is taking around a day. What happens after a year?

It may easily take more than 5 days. If it grows huge, can the current software handle it? 

What is the estimation of the blockchain to grow in next 10 years? Is it possible to split the blockchain into multiple blockchains? Could it become a blocker for Bitcoin adoption?
Actually, as Satoshi explained in his paper, you can use a Simplified Payment Verification (SPV) client which would only require you to download the headers of each block.

From the paper itself:


  As such, the verification is reliable as long as honest nodes control the network, but is more vulnerable if the network is overpowered by an attacker. 


So if you're not mining, and the network is overpowered by honest nodes (as it should always be for Bitcoin's integrity) you don't need to use a full node.

Bitcoin-QT is a full node probably because it's the official client and it bundles all the features since day one. Using something like MultiBit, which is an SPV client, would offer you the same exact amount of security as Bitcoin-QT.

So no, the increasing size of the blockchain is not really a blocker for Bitcoin's adoption because only miners would need the entire blockchain data.