It appears that in order to save up on Long Term Capital gain, you have invested the proceeds partly in underconstruction property and partly in CG Bonds.
Now as per the act, you can claim the exemption if you buy a new house property within 2 years or construct within 3 years from the date of sale.
Since you are planning to buy a ready to move in property, you should make sure that you buy the property within 2 years from the date of sale of your earlier property which will be ending in May'16.
In case of sale of your under construction property, you will be required to pay Short Term Capital Gain Tax.
Trust this clarifies your query.
Feel free to get back/ call back for any further clarifications.
Rohit R Sharma
BCOM, ACA, LLB - GEN, CERT. FAFP