Moved to Business > ePO for better attention.
What is the challenges we will face if we will plan to upgrade the ePO 4.5 to ePO4.6 on our current server harware configuration
I would expect you to run into serious performance issues, and almost certainly drive space issues - I'm surprised you're not already experiencing problems.
if you haven't already done so, please read the ePO hardware sizing guide, which can be found here: PD23282 - it will hopefully give you an idea of what you need.
Actually I'm amazed that with 10,000 nodes, your database is only 6GB. You are most definitely going to need more drive space for the database alone. Much more - the problem is that its not recommended to shrink your database- this could cause performance issues later down the road. Its better to host your db on a drive that will have space to grow.