Gerald Tan :
currently am using the i5 2400, with h61 u3s3 mobo.
should i wait or carry on with the upgrade considering the values for it on the market. ?
Without OC, an i5-4670 would be around 25% faster than your i5-2400, which is definitely NOT worth it IMO.
Unless you add OC or step up to i7 or are currently running into irritating or unbearable CPU-bound usability issues, you can probably wait for Skylake in 2015 or at least the platform (97-series chipsets) refresh with Haswell-Refresh if you cannot wait until Broadwell-K in late-2014.