Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_2_1 like Mac OS X; en-gb) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8C148 Safari/6533.18.5)
I would assume before the next iPhone arrives in July. Apple have released test versions of iOS 4.3 to developers, which is expected to arrive "soon". It will most likely coincide with the launch of the Verizon iPhone 4.