Depending on your needs all your options are viable.
1)If you plan to live in an EC to enjoy the condo facilities, and your finances allows it go ahead, there a few EC launches right now and you can take a look around. you would only need to sell off your hdb in 6 months after it has TOP.
2)Same as option 1 with the execption that you have a wider choices based on your budget and expected cash returns after selling your hdb.
3) If your finances allows it, do consider it. Your hdb unit must already meet the MOP and also you can choice either to buy a small 1/2 bed unit to rent out so the quantumn loan won't be alot or buy a bigger unit so you can rent out your HDB.
There are alot of options for you only to see which fits you. call me or lets fix a appointment for a cup of coffee so we can discuss it out further.