in my contry we have just GSM (global system for mobile) and soon we will have 3G .so for 3G service we will keep the same number?

Most probably your numbers will be same. Upgrading to3G should be a value addition like high speed data to your existing connection. In few cases, the SIM card needs to be changed. Overall it depends on how the telco is planning to upgrade and offer package.

Yes Same number should be used. But mostly you need to change the SIM. 

It depends on your strategy for numbering,

But more easier way is to use same numbers and even if the simcards are3G capable you don't need to change them.

Dpends on your plan, and the country you are deploying3G.

In General many operators do not deply3G on each2G site ... they deploy3G on asites where high PS (and CS too) traffic is expected or happening.

My advice is deply3G on as much as possibe on2G sites.

One more thing you can check the CS/PS traffic on2G side and rank the CS/PS traffic, and deply the3G on the most demand CS/PS traffic on the2G sites (especially for PS traffic).

YAH YOU CAN USE THE SAME NO.BUT THE PLANS C AN ALSO BE USED AS BY SETTING THE THE NETWORK MODES YOU CAN USE DIFFERENT PLANS.

it depends on the policy of the service providers in your country, we will need only to have a mobile phone that works with the new3G frequency bands,

but i think it's normal to provide the services of3G and LTE on any mobile number, but at the end you need to have the compatible phone 

it might be required to change your sim card, but not the number

Yea usually u will keep ur number because the3g in the first time of installation is used for internet packets not for making a call caz when u r connected to3g for internet browsing and someone called u it converted to2g after u finish ur calling u will return to3g but in time there is apolicy allowed u to call and browse internet in the same frequansy3g and the problem comes in4g it need a mobile phone compitable with the operater company that install the system u must ask the operator in ir cuntry about the frequancy that uses in4g to bought a mobile computable with this caz its hardware not software