the absence of parenthesis in Python

Sorry, but the premise of the question is a bit unclear to me. For example, Python requires parentheses on function calls (print("Hello")), while Perl makes them optional in many cases (print "Hello", map $_+1, 2, 3, ...). It is true that in Python, flow control statements such as if don't normally have parens around the condition, although you can add them - AFAICT, "if(b > a):" is the same as "if b > a:". It's also possible to write multiple statements on one line in Python. Perl does require the parentheses in such statements, except of course in statement modifiers. Also, Perl requires the braces around code blocks following if (...), unlike in other languages like C where they can be omitted for single statements.

Perl seems to encourage the condensing of complex code to one-liners

I don't think this is true. Perl simply offers the programmer a great amount of flexibility, and what the programmer does with that is up to them. Compared to other languages, writing Perl in a certain style consistently requires more discipline, partially because Perl code formatters like perltidy aren't perfect. I'm not saying that people who write "condensed" code are undisciplined - the fact that Perl gives a great amount of power, and that some people have taken the art of golfing to a new level using that power, is very cool! I'd say Perl encourages creativity - whether or not "creative" coding is appreciated in certain contexts, such as writing code other people need to work with, is another question ;-)

the condensing of complex code

I get the feeling that your question is more about this than about parentheses and brackets?

Could a future version of Python finally adopt parenthesis?

If you're asking whether a future version of Python would allow for more condensed code, then I'm willing to bet the answer is no - the strict indentation rules of Python is one of the major aspects of the language.

I don't really understand why Python would ultimately not want to use parenthesise.

Perhaps this helps: PEP 20 - The Zen of Python and PEP 8 - Style Guide for Python Code.

Update:

Update
I have to apologise. I don't mean parenthesis, instead I mean nesting using curly brackets.

Regarding whether Python will introduce something like blocks (by which I mean, blocks that can be used on a single line), see my answer above. Regarding Perl, see Acme::Pythonic ;-)