Borland didn't die because of Delphi
They died because of what they tried to DO with Delphi... i.e. follow Microsoft down the .NET route, believing the MS BS that .NET was the way of the future (back when MS still beliebved it themselves I guess). But no-one can compete with Microsoft in the .NET space because Microsoft have finally managed to close the gap between language, IDE and runtime framework. Anyone else is always going to be playing a very obvious game of catch-up in that space.
Borland compounded their error by trying to make Delphi and the VCL a single-source language for Win32/.NET applications, ignoring the very different nature of native code and managed code that makes any such attempt a hopeless mess, and relying on their cash cow to keep the $$$'s rolling in with minimal investment/development $$$'s while they went chasing after the ALM market.
Borland realised their mistake, but too late. They eventually refocussed on native code development but by then needed to sell off the family silver to keep the bailiffs away from the door. So Delphi got snapped up by Embarcadero where it is enjoying something of a rennaissance as it continues down it's renewed native code development focus.
Microsoft have pretty much abandoned native code development tools, despite the fact that native code itself will not be going away any time soon (most new API's even in Windows 7 are native code), leaving a HUGE open goal for commercial, native code alternatives.
As for Open Source (for Windows development, specifically), the people looking for high productivity native code development tools for RAD desktop application development aren't looking at Open Source, or if they are, they quickly find that whilst there are Open Source languages and IDEs, there aren't really any viable native code Open Source frameworks ready for prime time in order to facilitate the RAD approach they want/need.
So whilst it's sad for Borland, it's pretty much the best possible outcome for Delphi.
Delphi is left sitting pretty, whilst Borland pay the price for their gullibility without dragging Delphi down with the sinking ship.